1. Field of the Invention
This invention pertains in general to the field of breathing apparatuses. More particularly the invention relates to a device, aggregate and/or method for providing a gasified anesthetic agent by means of a breathing apparatus.
2. Description of the Prior Art
Certain anesthetic vaporizers for liquid anesthetic agents are known from the prior art.
For instance, in U.S. Pat. No. 6,230,666 an anesthetic vaporizer is disclosed for an anesthesia machine.
However, anesthetic vaporizers are hitherto provided as integrated units in rather costly anesthesia workstations. In addition, there have been previous systems based on intensive care ventilators with added anesthesia capability, such as the Siemens-Elema Servo Ventilator 900C. However, these systems were not providing a volume neutral delivery of gasified anesthetic agents, due to an additional fresh gas flow provided in addition to an inspiratory flow of gas from the ventilator. The anesthetic agent supplied to the patient needs a carrier gas, usually a mixture of O2 and/or air and/or nitrous oxide, into which the anesthetic agent is gasified, usually from a liquid state. The gasified anesthetic agent is then added, together with a volume of the carrier gas, to a flow of breathing gas in a breathing circuit, to which the patient is connected. This volume is often larger than the volume of carbon dioxide removed from the breathing circuit in the carbon dioxide absorber, and the surplus will be sent into to the evac system, usually via a so called pop off valve relieving pressure over a certain threshold in the breathing circuit. The flow of carrier gas is the aforementioned fresh gas flow, and is provided to pass an anesthetic gasifier unit. Therefore, the gasified anesthetic agents are not provided in a way of volume neutral delivery with reference to the flow of breathing gas. However, non-volume neutral delivery of anesthetic agent often results in a loss of anesthetic agent to the evac system due to the extra volume.
Thus, there is a need for a new anesthetic gasifier unit or aggregate having modular capabilities for use with breathing apparatuses, such as intensive care ventilators, and providing a substantially volume neutral supply of anesthetic agent to a breathing gas delivered to a patient.
Anesthetic vaporizers for direct injection of a liquid anesthetic agent into a mainstream of gas delivered to a patient are for instance disclosed in U.S. Pat. No. 6,155,255 of Hans Lambert. However such mainstream arrangements have some major disadvantages. One issue is that liquid agent that is not fully vaporized may be present in the mainstream to the patient. Droplets or aerosol of liquid anesthetic agent leads to several complications. One complication is that gas analyzers may render less reliable measurement results for non gaseous components. Thus, a feedback control of the agent concentration may be erroneous and the patient safety may be risked by too high administered anesthetic drug concentrations, i.e. the mainstream vaporizer of U.S. Pat. No. 6,155,255 may provide non-desired high doses. Another issue is handling safety of the device of U.S. Pat. No. 6,155,255. Clinical care personal may disconnect the tubing in which the device of U.S. Pat. No. 6,155,255 is arranged while it still is injecting liquid anesthetic agent. The anesthetic agent will thus be delivered uncontrolled to the surrounding environment by continued injection of liquid anesthetic agent. In this case, persons in the ambient environment, risk being subjected to the anesthetic agent, which might have dire health consequences.
Thus, there is also a need of providing an anesthetic delivery device for gaseous anesthetic agents having improved safety. Safety includes patient safety and/or safety of clinical personal, as well as reliability of the apparatus.
Hence, an improved anesthetic gasifier unit or modular aggregate comprising such an anesthetic gasifier unit would be advantageous and in particular allowing for increased flexibility, cost-effectiveness, patient safety, user friendliness and safety, and/or efficiency would be advantageous.